Heat can be transported from low temperature reservoirs, such as from ambient outdoor air, to high temperature reservoirs, such as to an indoor building space, by using mechanical and/or electrical energy input to a device such as a heat pump. Heat pumps can use an evaporator to remove heat from air. Operating temperatures of an evaporator of a heat pump evaporator are typically lower than the temperature of the air. If the temperature of the evaporator is below the dew point of the air, moisture in the air can condense on the evaporator surface. Moreover, if the air temperature is below the freezing point, the condensed moisture on the evaporator surface can turn to ice.
The efficiency of the heat pump can suffer if ice formation on the evaporator surface occurs. That is, as ice forms on the surface of the evaporator of the heat pump, the efficiency of the heat pump can be reduced. When ice formation occurs, it can be necessary to perform defrosting of the evaporator surface to melt the ice that has formed.